*{
    padding:0;
    margin: 0;
}
.box{
    width:300px;
    display: grid;
    grid-template-columns: repeat(3, 100px);
    grid-template-rows: repeat(3, 100px);
    margin:100px auto 0;
    grid-gap:1px ;
    background: yellow;
}
.item{
    background: red;
  
    box-sizing: border-box;
}
.item1{
    background: blue;
    box-sizing: border-box;
    grid-column-start: span 2;
}
.item-two{
    display: grid;
    grid-template-rows:50px 50px;
    box-sizing: border-box;
    row-gap:1px;
}
.small-item{
    background: pink;
    box-sizing: border-box;
}